Transmitting Apparatus and Retransmitting Method

1. A method of retransmitting a protocol data unit (PDU) in a transmitting apparatus of a wireless communication system, the method comprising: fragmenting at least one automatic repeat request (ARQ) block that is included in a first PDU into a plurality of ARQ sub-blocks; allocating at least one ARQ sub-block of the plurality of ARQ sub-blocks to a payload of a second PDU; allocating a first field representing a sequence number of the first ARQ sub-block belonging to the payload of the second PDU to a header of the second PDU; and transmitting the second PDU.

2. The method of claim 1 , further comprising allocating a second field representing whether the payload of the second PDU includes a last ARQ sub-block to the header of the second PDU.

3. The method of claim 1 , wherein the allocating of the at least one ARQ sub-block comprises: allocating other part of the plurality of ARQ sub-blocks to a payload of a third PDU.

4. The method of claim 1 , wherein the fragmenting of at least one ARQ block comprises generating the plurality of ARQ sub-blocks by fragmenting the ARQ block in a fixed size.

5. The method of claim 1 , further comprising allocating a second field representing whether the second PDU is a rearranged PDU to the header of the second PDU.

6. The method of claim 1 , further comprising allocating a second field representing a sequence number of the ARQ block to the header of the second PDU.

7. The method of claim 1 , further comprising allocating a second field representing fragmentation information of a service data unit (SDU) that is packed in the first PDU to the header of the second PDU.

8. The method of claim 1 , further comprising, when the payload of the second includes at least one SDU or SDU fragment, allocating a second field representing a length each SDU or SDU fragment to the header of the second PDU.

9. The method of claim 1 , wherein the at least one ARQ block comprises a first ARQ block from a first connection and a second ARQ block from a second connection, the plurality of ARQ sub-blocks comprise a plurality of first ARQ sub-blocks in which the first ARQ block is fragmented and a plurality of second ARQ sub-blocks in which the second ARQ block is fragmented, the method further comprises allocating at least one header block to the header of the second PDU, the at least one header block comprises at least one first header block corresponding to the first connection and at least one second header block corresponding to the second connection, and the allocating of the first field comprises allocating the first field to each of the first and second header blocks.

10. The method of claim 9 , further comprising allocating a second field representing whether the payload of the second PDU comprises a last ARQ sub-block to each of the first and second header blocks.

11. The method of claim 9 , further comprising allocating a second field representing whether the second PDU is a rearranged PDU to each of the first and second header blocks.

12. The method of claim 9 , further comprising allocating a second field to each of the first and second header blocks, the second field representing an identifier of connection for an ARQ sub-block that is included in a corresponding header block.

13. The method of claim 9 , further comprising allocating a second field to each of the first and second header blocks, the second field representing whether another header block exists after a corresponding header block.

14. The method of claim 1 , wherein the first PDU is a PDU that fails in initial transmission.

15. A method of retransmitting a PDU in a transmission apparatus of a wireless communication system, the method comprising: fragmenting at least one ARQ block that is included in a first PDU into a plurality of ARQ sub-blocks; generating a second PDU from at least one ARQ sub-block of the plurality of ARQ sub-blocks; and transmitting the second PDU, wherein the second PDU comprises: a header; and a payload comprising the at least one ARQ sub-block, wherein the header comprises a first field representing whether the payload comprises a last ARQ sub-block.

16. The method of claim 15 , wherein the header further comprises a second field representing a sequence number of the first ARQ sub-block belonging to the payload.

17. The method of claim 15 , wherein the header further comprises a second field representing whether the second PDU is a rearranged PDU.

18. The method of claim 15 , wherein the header further comprises a second field representing a sequence number of the ARQ block.

19. The method of claim 15 , wherein the header further comprises a second field representing fragmentation information of an SDU that is packed in the first PDU.

20. The method of claim 15 , wherein, when the payload of the second includes at least one SDU or SDU fragment, the header further comprises a second field representing a length of each SDU or SDU fragment.

21. The method of claim 15 , wherein the fragmenting of at least one ARQ block comprises generating the plurality of ARQ sub-blocks by fragmenting the ARQ block in a fixed size.

22. A transmitting apparatus of a wireless communication system, comprising: a refragmentation unit that fragments at least one ARQ block included in a first PDU into a plurality of ARQ sub-blocks and that allocates at least one ARQ sub-block of the plurality of ARQ sub-blocks to a payload of a second PDU; a PDU generator that allocates a header including a field representing whether a payload thereof includes a last ARQ sub-block to the second PDU; and a transmitting/receiving unit that transmits the second PDU.

23. A transmitting apparatus of a wireless communication system, comprising: a refragmentation unit that fragments at least one ARQ block included in a first PDU into a plurality of ARQ sub-blocks and that allocates at least one ARQ sub-block of the plurality of ARQ sub-blocks to a payload of a second PDU; a PDU generator that allocates a header comprising a field representing a sequence number of the first ARQ sub-block belonging to a payload thereof to the second PDU; and a transmitting/receiving unit that transmits the second PDU.